FIG. 1.
Effect of anaerobic culture on the morphology of M. bovis BCG, M. tuberculosis, and M. smegmatis. (A) Longitudinal section of an M. bovis BCG bacillus cultured anaerobically for 6 months showing pronounced cell wall thickening (some cytoplasmic dehydration is evident). (B) Transverse sections of M. bovis BCG bacilli cultured anaerobically for 6 months. (C) Lack of cell wall thickening in low-OD aerobically cultured M. bovis BCG bacilli. (D) NLSPC M. bovis BCG bacilli showing the absence of cell wall thickening. (E and F) Cell wall thickening in M. tuberculosis following anaerobic culture for 1 month under mineral oil. (G) Aerobically cultured M. smegmatis. (H) M. smegmatis bacilli exhibiting cell lysis following 35 days of anaerobic culture. Bars, 200 nm except for panels C (100 nm) and G (400 nm). The bar in panel A is also valid for panel F; the bar in panel D is also valid for panel H.